1. Field of the Invention
The present invention relates to an information processing apparatus with power saving mode, and a control method and a communication apparatus therefor.
2. Description of the Related Art
An information processing apparatus with power saving mode is known (see, for example, Japanese Laid-open Patent Publications Nos. 2009-151537 and 2008-181436).
A data processing apparatus disclosed in Japanese Laid-open Patent Publication No. 2009-151537 (corresponding to U.S. Patent Application Publication No. 20090164816 A1 ) has a main CPU and a sub CPU. In the power saving mode, the main CPU is supplied with no power or supplied with reduced power as compared to that in a normal power mode, and the sub CPU responds to incoming packets received through a network.
However, it is difficult for the sub CPU to respond to all the incoming packets since the sub CPU runs at a reduced clock rate in the power saving mode. Thus, after return to the normal power mode from the power saving mode, the main CPU responds to packets to which the sub CPU could not respond.
Generally, however, it takes a slight time for the main CPU to completely function in the normal power mode from start of power supply to the main CPU. In other words, there is idle time until the main CPU returns to the normal power mode from the power saving mode.
If packets are supplied to the data processing apparatus through the network during the idle time, a packet reception failure can occur.
To eliminate such a problem, the information processing apparatus disclosed in Japanese Laid-open Patent Publication No. 2008-181436 stores, into a memory, packets received through the network while the main CPU is being changed from the power saving mode to the normal power mode, thereby preventing a packet reception failure from occurring while the power saving mode is being returned to the normal power mode.
However, responses to incoming packets cannot be made during the idle time until the main CPU becomes able to completely function in the normal power mode.